This application relates to fiber devices with fibers engaged in grooves on a substrate. Fibers may be positioned into grooves formed into a surface of a semiconductor substrate to form various fiber devices. Typically, the placement of fibers into the grooves is performed manually by an operator. The final alignment of each fiber is dependent upon the individual skill of the operator.
Optical fibers are used to guide light from one location to another. The construction of a typical fiber includes a glass core that is surrounded by a glass cladding layer, the glass cladding layer is surrounded by a protective xe2x80x9cbufferxe2x80x9d layer (e.g., an acrylate-based plastic coating). The refractive index of the fiber core is higher than that of the cladding layer to confine the light. Therefore, light rays coupled into the fiber core within a maximum angle with respect to the axis of the fiber core are totally reflected at the interface of the fiber core and the cladding. This total internal reflection provides a mechanism for spatially confining the optical energy of the light rays in one or more selected fiber modes to guide the optical energy along the fiber core.
The guided optical energy in the fiber, however, is not completely confined within the core of the fiber. A portion of the optical energy can xe2x80x9cleakxe2x80x9d through the interface between the fiber core and the cladding via an evanescent field that essentially decays exponentially with the distance from the core-cladding interface. This evanescent leakage may be used to couple optical energy into or out of the fiber core, or alternatively, to perturb the guided optical energy in the fiber. A portion of the buffer and the fiber cladding may be removed and polished to form a coupling window to allow for optical access to the fiber core via an evanescent field of a guided mode supported by the fiber.
This application describes several embodiments for xe2x80x9ctension-assistedxe2x80x9d alignment and mounting of a fiber in a groove formed in a substrate. In the described embodiments, prior to placing the fiber in a corresponding groove, the fiber is tensioned in a controlled manner. The fiber under tension is then aligned and positioned in the groove. In some of the embodiments, the fiber is also wrapped around a contour of the groove. An adhesive material is then applied in the groove to fix the position of the fiber after the adhesive is cured.
In some of the embodiments described, a suitable adhesive material is applied in the groove prior to mounting the fiber in the groove. In this case, before the adhesive is hardened, the fiber held under tension is placed in the adhesive within the groove and is wrapped around a contour of a groove. After the adhesive is cured, the fiber is fixed in the groove. A typical adhesive used is a ultraviolet-cured (UV-cured) epoxy that is cured after the fiber is positioned into the groove by the application of a UV light.
In some cases, after the fiber is mounted and fixed in the corresponding groove, the fiber is polished to remove a portion of the fiber cladding and/or a portion of the fiber core by an appropriate process such as a chemical-mechanical planarization (CMP).
In some of the described embodiments, tension-assisted mounting is used for aligning and mounting several fibers roughly simultaneously, i.e., aligning and placing several fibers into a parallel array of grooves formed in a substrate. Following placement into the grooves, the fibers can be attached to the substrate grooves by an adhesive that may be cured in all of the grooves roughly simultaneously (e.g., by applying a UV-light to a UV-curable adhesive). This is an advantage, since the curing time for some adhesives is several minutes. Following attachment to the substrate, the array of fibers may be polished roughly simultaneously, i.e., removing a portion of the fiber cladding and/or the fiber core of each fiber in a wafer-level fabrication process to achieve a high throughput.
The described embodiments are applicable to operations that may be automated to ensure repeatability, increase quality, and increase the throughput in fabrication of fibers on substrates. Moreover, the described embodiments are applicable to placing and handling fibers with machine automation.